L0301P3 - Biomolecules of Life
__TOC__ Water *polar molecule (hydrophilic) As a solvent *main solvent within cells *medium in which all solute molecules are transported *makes up 70% of the body mass **47% Intracellular **23% Extracellular ***6% Blood plasma and 17% Interstitial Fluid *dissolves ionic molecules, or larger molecules ionic in nature (proteins) Ionisation of Water *essentially a neutral molecule but is amphiprotic **act as a proton donor - OH- **act as a proton acceptor - H3O+ Reactions with Water *produced - condensation *required - hydrolysis *added - addition/hydration *taken away - elimination Flickering Cluster Model *rapid state of flux *clusters constantly growing, shrinking, breaking and reforming *~ 85% are bonded in clusters - forms hydrogen bonds with other molecules Macromolecules *non-mineral component of living tissues *formed by covalent bonds *contain many functional groups that affect their structure and function *monomers form polymers by condensation reactions *polymers broken down in to monomers by hydrolysis reactions Proteins Functions *Movement (Muscle proteins) *Enzymes *Support and protection (keratin) *Transport *Defence (antibodies) *Regulation (hormones) Structure *Polypeptide chains of proteins are folded into specific three-dimensional shapes *Structure is classified into 4 levels: **Primary structure ***the sequence of amino acids bonded by peptide linkages **Secondary structures ***maintained by hydrogen bonds between atoms of the amino acid residues **Tertiary structure ***generated by bending and folding of the polypeptide chains **Quaternary structure ***the arrangement of polypeptides in a single functional unit consisting of more than one polypeptide subunit Carbohydrates Structure *predominantly in its cyclised form *(CH2O)n, may contain nitrogen, phosphorus and sulphur Functions *Storage/source of energy (starch) *Protein Sparing (having enough carbs spare the proteins from being used) *Providing bulk in the diet *Structural (cellulose) *Aiding in the synthesis of other substances (glycolipids, glycoproteins, non-essential amino acids by providing carbon skeleton) *polymers have variable molecular weights unlike proteins etc *polysaccharides are also known as glycans *differ from each other by: **what monosaccharide units **length **types of bonds linking units **degree of branching *when body is lacking nutrition, proteins are metabolised for energy instead **Under normal circumstance, the existence of carbohydrates (and the fact that they can be stored) means that they are preferentially metabolised. Common Polysaccharides Starch *two types *can be linear or branched Glycogen *branched *the form in which carbohydrates are stored in humans Cellulose *linear *humans do not have the enzymes necessary to break down cellulose and thus it cannot be used for an energy source Peptidoglycan *component of the cell wall of bacteria *linear polymers *antibiotics - prevent cell walls of bacteria to be made by interfering with the peptidoglycan Glycoconjugates: *Glycosaminoglycans **large polysaccharides **attach to extracellular proteins **family of linear polymers made of repeating disaccharides **one of the 2 monosaccharides is always either: ***N-acetyl glucosamine ***N-acetyl galactosamine **attach to extracellular proteins to form proteoglycans **at least one of the sugars has a negative charge due to a sulphate or carboxyl group   *Glycolipids **membrane lipids bound with oligosaccharides (hydrophilic head group) **examples ***Gangliosides: membrane lipids of eukaryotic cells ***Lipopolysaccharides: dominant surface feature of some gram- negative bacteria Lipids Functions *energy source (most concentrated energy supply) *storage of energy (85% of body’s’ energy) *structural components in membranes *signalling molecules *enzyme cofactors *synthesis of bile acids *vitamins and vitamin transport *insulation *padding *enhances palatability of food *satiety Triacylglycerols *also known as triglycerides *1 glycerol and 3 fatty acids *joined by ester linkages *saturation: **saturated fatty acids ***hydrocarbon chain with no double bonds = no bend in the chain **unsaturated fatty acids ***one or more double bonds ***bend the chains, making close packing less possible and thus usually liquid at room temperature Phospholipids *phosphate head **hydrophilic *glycerol *2 fatty acid tails **hydrophobic Cholesterol *synthesised in the liver *role in cell membranes *used to synthesise: **bile acids (used in fat absorption) **other steroids **vitamins